NG 900/9-3 Vacuum Lines

Overview

Vacuum lines and PCV components should be inspected every 30k miles or more often, and replaced as needed. Rubber hoses become brittle with age, and deterioration and small cracks can be hard to see. Original vacuum hoses are 4-mm inside diameter (ID), same size as most of the wiper washer hoses. The same rubber hose is also used in the secondary air injection (SAI) system on n/a models. These were replaced around 100k miles, some for the second or third time.

Replacing

Parts

• Vacuum Hose - Figs. 1 and 2
  • 1a - 240 mm
  • 1b - 60 mm
  • 2 - 220 mm
  • 3 - 400 mm
  • 4 - 800 mm

Fig. 1 - Vacuum hose lengths

Fig. 2 - Throttle body labels

• PCV Components - Fig. 3
  • a - Valve cover bushing #7515190
  • b - PCV nipple #9165903
  • c - Rubber hose #9189465
  • d - Generic 4-mm rubber hose, NAPA H-459
  • e - PCV check valve #7521313

Fig. 3 - PCV Components

PCV Valve Hoses

Fig. 4

Part of the positive crankcase ventilation system. This line leads from the valve cover to the engine intake. In the picture at left, the stock 4-mm rubber hose is was replaced by a 4.8-mm reinforced fuel line. It is less likely to clog, and lasts longer.

The check valve (PCV valve) needs periodic replacement. The plastic valve cover nipple, grommet (bushing) and larger diameter hose may also need replacement if leaking oil.

Fig. 4 - PCV Valve Hoses

MAP Sensor

Fig. 5

Not the same part number and material as the other hoses (possibly silicone rubber from the factory). It seems more durable, and should probably only be replaced by a compatible silicone hose. It leads to the manifold air pressure (MAP) sensor.

Fig. 5 - MAP Sensor hoses

Fuel Pressure Regulator

Fig. 6

From the throttle body to the fuel pressure regulator (FPR). The FPR is on the driver side of the fuel rail, below the charge air pipe and behind a connector bracket. The view on the left is from the driver side fender, and after unplugging the three connectors. This line can be hard to inspect and replace because most of it is hidden under fuel rail wiring.

Fig. 6 - Fuel Pressure Regulator hoses

Charge Air Bypass Valve

Fig. 7

Runs along the "charge air pipe" to the turbo bypass valve (BPV) at the front of the engine compartment. This is the longest of the four hoses.

Fig. 7 - Charge Air Bypass hose

Evap System Purge Valve

Fig. 8

The purge valve hose for the Evaporative Emission System connected to the throttle body is not an actual vacuum line (different size and material). It allows fumes to be sucked from the charcoal canister in the wheel well into the intake and burned. However, if the hose is broken, or the purge valve faults, the effect can be the same as a vacuum leak.

Fig. 8 - Evap System Purge Valve